1. Field of the Invention
This invention relates to a swim monofin that is adapted to be mounted on the feet of a swimmer for propelling the swimmer through the water, and more particularly to a monofin having feet securing portions that can be selectively and variably positioned to accommodate the physical attributes and preferences of a particular user.
2. Description of the Prior Art
Monofins are primarily used as a competitive swim fin training device. They have applications in, other areas as well, including rehabilitation, scuba and snorkel diving, and high-speed swimming.
It is well known in the prior art to form a monofin for a swimmer, wherein the monofin has two foot-receiving pockets. In the prior art, the receiving pockets are typically formed in the same fashion as foot-receiving pockets on traditional single-foot swim fins. Additionally, the prior art positions the foot pockets in side-by-side, parallel configuration to hold the feet substantially adjacent and parallel.
For example, U.S. Pat. No. 3,934,290 to LeVasseur discloses a swim monofin designed for use as part of a larger swimming apparatus. The monofin has two discrete foot-receiving pockets that hold the feet of the user together in adjacent and substantially parallel fashion. With the user's legs and feet extended, the monofin is substantially aligned with the plane of the swimmer's body. The monofin has conduits in its forward section to divert water rearwardly and outwardly from the fin.
U.S. Pat. No. 4,781,637 to Caires discloses a swim monofin having a wing-like blade, with the blade having a generally tear-dropped cross-section similar to an aircraft wing. The blade comprises a generally flat planar surface, and is designed to produce equal resistance in the extending and retracting kicking motions. The hydrofoil shape directs the flow of water rearwardly and substantially parallel to the swimmer's path. The user's feet are held together in adjacent and parallel configuration, with the soles of the feet roughly defining a common plane.
U.S. Pat. No. 4,541,810 to Wenzel discloses a monofin having an integral foot-receiving pocket designed to accommodate both feet, together and in parallel position, in the single pocket. The fin has an inner stiffener to maintain its shape during use. The fin is specifically designed to maintain constant resistance through the extending and retracting kicking motions. Water passing over the fin is diverted rearwardly and inwardly.
U.S. Pat. No. 3,344,449 to Grilli discloses a mermaid-shaped swimming tail. The tail is designed to resemble a mermaid's fishtail. The fin of the tail is generally triangular-shaped, and in one embodiment has reinforcing ribs to maintain the fins flat shape during kicking. A complex system of these reinforcing ribs allows the fin to collapse in retracting stroke but maintains the fin rigidly flat during the extending stroke. Instead of having two foot pockets, Grilli discloses a single foot boot which positions the feet in adjacent and parallel position. This foot boot inhibits proper angular motion of the foot and ankle.
A prior art monofin marketed under the mark, "Hyperfin Fibra", and as embodied in a published brochure discloses a monofin having a large, generally triangular shape. The fin is large in front-to-back length, with a length of similar size to the width. The foot pockets are an integral part of the monofin and have pockets similar in construction to those found on regular one-foot swim fins. The "Hyperfin" pockets appear to hold the user's feet in side-by-side and parallel relationship.
There are two main problems with the monofins of the prior art. The first problem is the parallel positioning of the feet. The second problem is holding the feet flat relative to each other, i.e., positioning the feet so that their soles are coplanar. The parallel, coplanar positioning of the feet interferes with proper execution of the dolphin kick, which is the most common swimming kick used with monofins.
When executing a proper dolphin kick, the upper legs are held together while the feet are positioned with the ankles spaced further apart than are the toes, resulting in a somewhat "pigeon-toed" stance. This toed-in position allows the swimmer to move his legs and feet in a smooth, efficient motion.
Additionally, during execution of a proper dolphin kick, the soles of the feet do not form a common plane. Instead, the instep of each foot is forced downward relative to that foot's outer edge. Thus, the sole of each foot defines a separate plane from that of the other foot, with the two planes intersecting to form a shallow angle between the two feet.
Holding the feet flat and parallel to each other, as is required with all prior art monofins, causes the swimmer's legs to bow outwardly at the knees, increasing strain along the knee during swimming. Furthermore, such positioning of the feet forces the swimmer to primarily use the weaker inner thigh muscles, as opposed to the larger and stronger outer thigh muscles.
The optimum positions of and distance between, the feet during a dolphin kick vary according to the individual swimmer, taking into account such factors as the swimmer's foot size and ankle flexibility. Monofins having foot pockets permanently fixed in standard positions cannot be tailored for optimal use by particular swimmers.
In theory, monofins should be of great use for therapeutic conditioning and rehabilitation. However, since prior monofin designs are flat and have foot pockets that hold tile feet parallel, their use places large amounts of Stress on the user's lower back and knees. The stress is so great that a good portion of initial monofin race training for competitive athletes is devoted to specific muscular conditioning designed to limit knee and back injury. Paraplegics and those with limited lower back and leg strength, who in theory should be able to benefit greatly from monofin exercises, usually can not Use existing monofins due to the difficulty in overcoming the drag of the blade during the retracting stroke.
The present invention overcomes several of the inherent disadvantages and problems associated with the prior art devices.